The ONU optical transceiver is used on the ONU device. Generally,
it consists of the following parts: the burst mode laser drive, the
receiving end limiting amplifier, the BOSA, the MCU, the APD boost
circuit and so on.

The originator uses a burst mode driver to drive the laser. The
timing sequence: for EPON, Ton/Toff<30ns is required, and for
GPON, Ton/Toff<12.8ns is required.

The receiving end is continuously received, and a special amplitude
limiting amplifier is needed to amplify the electrical signal
converted by the PD. The receiving end components are composed of
two kinds of APD-TIA and PIN-TIA.

Now the common encapsulation structure of the ONU optical
transceiver is SFF structure, and the shape of the SFF and the
definition of the pin foot follow the SFF multisource protocol.
Generally, it is divided into two structures: 2x5 and 2x10. Optical
structure is divided into two types: Pigtail Receptacle and
Pigtail. And there two fiber optic pigtail types: SC/UPC (blue) and
SC/APC (green). Pigtail length is variable. Generally not more than
1m.